Instantaneous trip means

ABSTRACT

The instantaneous trip means for a circuit breaker is constructed with an electromagnet having a movable armature biased away from a stationary yoke. A biasing spring for the armature acts on the armature through a pivoted trip lever. One end of the biasing spring is connected to the trip lever at a point very close to the pivot for the trip lever, and the line of action for the spring is so positioned that as the armature moves toward tripping position increased loading of the biasing spring is negligible thereby permitting extremely rapid movement of the armature to its tripping position.

Heberlein, Jr. et al.

[451 Oct. 29, 1974 INSTANTANEOUS TRIP MEANS Inventors: Gustave E.Heberlein, Jr., Chalfont; Frank W. Kussy, l-laverford, both of Pa.

l-T-E Imperial Corporation, Spring House, Pa.

Filed: Dec. 27, 1973 Appl. No.: 428,884

Assignee:

References Cited UNITED STATES PATENTS Lloyd 335/176 Jencks et al.335/176 Primary Examiner-Harold Broome Attorney, Agent, orFirm-Ostrolenk, Faber, Gerb & Soffen [57] ABSTRACT The instantaneoustrip means for a circuit breaker is constructed with an electromagnethaving a movable armature biased away from a stationary yoke. A biasingspring for the armature acts on the armature through a pivoted triplever. One end of the biasing spring is connected to the trip lever at apoint very close to the pivot for the trip lever, and the line of actionfor the spring is so positioned that as the armature moves towardtripping position increased loading of the biasing spring is negligiblethereby permitting extremely rapid movement of the armature to itstripping position.

2 Claims, 2 Drawing Figures PATENTEUUEI 29 nan 1 INSTANTANEOUS TRIPMEANS This invention relates to circuit breakers in general and moreparticularly relates'to magnetic trip means therefor.

Most relatively high current molded case circuit breakers are providedwith a so-called instantaneous trip means that automatically causesopening of the circuit breaker upon the occurrence of predeterminedfault current conditions. The instantaneous trip means usually consistsof an electromagnet having an armature that is normally restrained frommoving by a biasing spring. When the fault currents exceed apredetermined level, magnetic flux generated in the electromagnetstructure creates forces which overcome the armature biasing force andmove the armature to a tripping position.

However, even upon the occurrence of extremely high fault currentconditions, such as a phase-to-phase short in a circuit capable ofdelivering extremely high currents, opening of the circuit breaker isnot really instantaneous. One of the reasons for delay in operation ofthe instantaneous trip means is the fact that as the armature movestoward tripping position there is a significant increase in loading ofthe armature biasing spring, with this increased loading serving toretard armature movement toward the tripping position.

In order to overcome this deficiency of the prior art, the instantinvention provides a mounting for the armature biasing spring, soconstructed that as the armature moves from its normal position to itstripping position, increased loading of the armature biasing spring isminimized. This is accomplished by applying biasing forces to thearmature through a pivoted trip lever and by appropriately positioningthe line of action for the biasing spring. These biasing forces areprovided by a coiled tension spring, one end of which is secured to anadjustably positionable relatively fixed anchor, and the other end ofwhich is secured to the trip lever at a location very close to the pivotfor the trip lever. Positioning of the biasing spring is such that asthe armature moves from its normal to its tripping position, theincrease in length of the spring is negligible, so that there is nosignificant increase inloading on the armature as it moves towardtripping position. Thus, this armature movement is very rapid.

Accordingly, a primary object of the instant invention is to provide anovel construction for the instantaneous trip means of a circuitbreaker.

Another object is to provide a magnetic trip means in which biasingforces acting on themagnetic armature are not increased substantially asthe armature moves toward tripping position.

Still another object is to provide a magnetic trip means of this type inwhich'the magnetic air gap remains fixed during adjustment of armaturebiasing forces.

A further object is to provide automatic trip means of this type whichis suitable for simultaneous multipole adjustments.

These objects as well as other objects of this invention will becomereadily apparent after reading thefollowing description of theaccompanying drawings in which:

FIG. 1 is a schematic of a circuit breaker including magneticinstantaneous trip means constructed in accordance with teachings of theinstant invention.

terminal strap 18. Contact 14 is operable into and out of engagementwith contact 13 by contact operating mechanism 20 which is connected tomovable contact arm 15 and is provided with manual operating handle 21.Contact operating mechanism is typically constructed with a trip-freespring-powered overcenter toggle and includes releasable latch means(not shown). Extension 22 of the releasable latch means for mechanism 20is normally restrained by transverse prov jection 23 of common tripperbar 25 that extends between all poles of circuit breaker l0 and ismounted on longitudinally extending pivot 24.

Another radial projection 26 of tripper bar 25 is positioned forengagement by leg 27 of trip lever 30 which is mounted at its mid-regionon pivot 28. The other leg 29 of trip lever 30 is bifurcated at its freeend so as to provide a passage for threaded rod 31. Calibrating nut 32is threadably mounted to rod 31 above lever section 29 and belowstationary abutment 35 having guide opening 34 through which the upperend of rod 31 extends. Magnetic armature 35 is fixedly secured to thelower end of rod 31 so as to be movable toward and away from generallyU-shaped magnetic yoke 36 having coil 17 wound about its web portion.

Coiled tension spring 37 biases armature 35 upward toward its normalposition shown in FIG. 1. One end of spring 37 is connected to movableanchor 38 on lever 29 and the other end of spring 37 is connected tocrank 40 at relatively stationary anchor 39 located near the free end ofcrank arm 41. Crank 40 is mounted to stationary pivot 43 and is providedwith follower arm 42 that is biased into engagement with cam 44. Thelatter is keyed to shaft 45 having manually operable adjusting wheel 46keyed thereto. Shaft 45 extends through all poles of circuit breaker 10and mounts cams corresponding to cam 44 of the other poles, so that aswheel 46 is pivoted there is simultaneous movement of the cams 44 in allpoles to simultaneously change the positions of their respective cranks40. It should now be apparent to those skilled in the art that aperipheral portion of wheel 46 is accessible for manual operation from aposition outside of the molded housing for circuit breaker 10.

Upon the occurrence of fault current conditions exceeding apredetermined level, magnetic flux generated in magnetic frame 35, 36 bycurrent flowing through coil 17 generates forces sufficient to overcomethe bi asing forces exerted by spring 37 and move armature 35 downwardtoward yoke 36. During this downward movement of armature 35 calibratingnut 32 on rod 31 also moves downward thereby engaging lever arm 29 topivot lever 30 in a counterclockwise direction. This causes lever arm 27acting through tripper bar projection 26 to pivot tripper bar 25 in aclockwise direction, moving latching projection 23 to the left clear oflatch means extension 22. This releases the latch of contact operatingmechanism so that the latter separates movable contact 14 fromstationary contact 13.

Because movable spring anchor 38 is located so close to trip lever pivot28 and because of the location of relatively stationary anchor 39 withrespect to pivot 28, as armature 35 moves from its normal position toits tripping position, spring 37 increases very little in length so thatthe additional loading thereof is negligible. That is, during thedownward stroke of armature 35 movable anchor 38 moves along an arcuatepath 51 (FIG. 2) about pivot 28 as a center toward the extension 52 of astraight line drawn between anchor 39 and pivot 28, until at thetripping position of armature 35 anchor 38 is at the phantom positionshown in FIG. 2. It is noted' that the total movement for anchor 38 issubstantially less than 90 and the distance between extension 52 andanchor 38 in the normal position of armature 35 is also substantiallyless than 90.

Although there have been described preferred embodiments of this novelinvention, many variations and modifications will now become apparent tothose skilled in the art. Therefore, this invention is to be limited notby the specific disclosure herein but only by the appending claims.

The embodiments of the invention in which an exclusive privilege orproperty is claimed are defined as follows:

l. A circuit breaker including cooperating contact means, an operatingmechanism for opening and closing said contact means, trip meansincluding an electromagnet comprising a relatively stationary sectionand an armature mounted for movement toward said rela tively stationarysection to a trip position from a normal position remote from saidstationary section, said armature moving to said trip position upon theoccurrence of fault current above a predetermined level, therebyautomatically actuating said operating mechanism to open said contactmeans, a trip member interposed be tween said armature and saidoperating mechanism, a spring means acting through said trip member tobias said armature toward said normal position, a pivot about which saidtrip member pivots as said armature moves from the normal position tothe trip position, a

relatively fixed anchor for one end of said spring means and anotheranchor connecting the other end of the spring means to the trip memberat a point very close to said pivot to minimize increased loading ofsaid spring as the armature moves toward the trip positiom' adjustablemeans to adjust biasing forces exerted by said spring means on saidarmature by repositioning the relatively fixed anchor without alteringthe normal position of the armature; said adjustable means including acam means selectively operable to reposition the relative fixed anchor;a pivotally mounted element which carries the relatively fixed anchor,said spring means biasing a follower portion of said element intooperative engagement with said cam means.

2. A circuit breaker as set forth in claim 1 also including calibratingmeans to establish the normal position of the armature without alteringthe biasing forces acting on the armature.

1. A circuit breaker including cooperating contact means, an operatingmechanism for opening and closing said contact means, trip meansincluding an electromagnet comprising a relatively stationary sectionand an armature mounted for movement toward said relatively stationarysection to a trip position from a normal position remote from saidstationary section, said armature moving to said trip position upon theoccurrence of fault current above a predetermined level, therebyautomatically actuating said operating mechanism to open said contactmeans, a trip member interposed between said armature and said operatingmechanism, a spring means acting through said trip member to bias saidarmature toward said normal position, a pivot about which said tripmember pivots as said armature moves from the normal position to thetrip position, a relatively fixed anchor for one end of said springmeans and another anchor connecting the other end of the spring means tothe trip member at a point very close to said pivot to minimizeincreased loading of said spring as the armature moves toward the tripposition; adjustable means to adjust biasing forces exerted by saidspring means on said armature by repositioning the relatively fixedanchor without altering the normal position of the armature; saidadjustable means including a cam means selectively operable toreposition the relative fixed anchor; a pivotally mounted element whichcarries the relatively fixed anchor, said spring means biasing afollower portion of said element into operative engagement with said cammeans.
 2. A circuit breaker as set forth in claim 1 also includingcalibrating means to establish the normal position of the armaturewithout altering the biasing forces acting on the armature.